Transfer sheet for transferring protective layer for photographic emulsion face and photomask with protective layer

ABSTRACT

The present invention is an invention providing a photographic emulsion surface protective layer transfer sheet, characterized by having on one surface of a releasable support a photographic emulsion surface protective layer which is adhesive and in an uncured state, and characterized in that the photographic emulsion surface protective layer in an uncured state comprises an ionized radiation-curable resin composition containing a hydrophilic group-containing monofunctional (meth)acrylate and a polyfunctional (meth)acrylate. This transfer sheet can have an adhesive layer excellent in scratch resistance, close adhesion to an emulsion surface and solvent resistance. Therefore, when this transfer sheet is used particularly for forming a protective layer on the emulsion surface of a photomask, the photomask capable of long-term consistent use is obtained.

TECHNICAL FIELD

The present invention relates to a transfer sheet used for transferringa protective layer to an emulsion surface of a photomask used inpatterning for a printed wiring board or a display panel or a photomaskfor photomechanical process, and a photomask having an emulsion surfaceprotected by the protective layer.

BACKGROUND OF THE INVENTION

As methods of protecting the surfaces of a wide variety of materials,there have so far been known a method of bonding a protective sheethaving an adhesive layer on one side of a thin film, such as a polyesterfilm, to the surface of a subject to protect and a method of forming aprotective layer on a film having releasability and transferring theprotective layer to the surface of a subject to protect through themedium of a pressure sensitive adhesive or a general adhesive. Themethod of transferring a protective layer to the subject surface via apressure sensitive adhesive or a general adhesive has an advantage thata thin protective layer can be formed, but it has also a disadvantage offailing to ensure sufficient strength in the transferred layer as awhole because the strength of the pressure sensitive adhesive or generaladhesive layer is lower than that of the protective layer. In order toovercome this disadvantage, various studies have been hitherto made.

For instance, Japanese Patent Laid-Open Nos. Sho 64-18698 and Hei4-201478 disclose the inventions in which the protective layer and theadhesive layer made up of an ionized radiation-curable resin which is asolid in an uncured state but has thermal plasticity is provided on thereleasable surface of a release sheet. In addition, Japanese PatentLaid-Open No. Hei 7-125496 discloses the transfer sheet having on a basefilm having releasability a subbing layer and a non-adhesive semi-curedlayer in a gelled state formed by irradiating a UV-curable resin coatingwith UV rays in an exposure dose about ⅓ to about ⅔ the exposure doserequired for completely curing the resin coating.

However, since the layer brought into contact with a subject ofprotection has a non-adhesive surface, those transfer sheets have adefect that heating treatment at the time of bonding or additionalapplication of a UV-curable resin to the subject surface is required forbonding the transfer layer to the subject surface and thereby theprotective layer formation process becomes complicated. Further, suchtransfer layers have a drawback of being unfit for transfer to materialssensitive to heat or solvents (e.g., emulsion surfaces of photographicfilms utilized as photomasks).

In addition, Japanese Patent Laid-Open No. Sho 61-258742 proposes amethod of transferring a protective layer having both releasability froma support and adhesion to the support to the surface of a subject toprotect through no medium or the medium of a combination of hot-sealableand pressure sensitive adhesive layers. In this method also, heating isrequired at time of transfer. The use of a pressure sensitive adhesivelayer with the intention of avoiding the necessity for heating caused adefect that the protected layer formed was poor in surface strength.

On the other hand, a photomask is generally made up of a transparentsubstrate and an emulsion layer provided thereon, and it is a sheetwherein patterns formed by a CAD system or the like are reproduced bysubjecting the sheet sequentially to an exposure with a device like aphotoplotter, development such as washing, fixation and drying. Thephotomask in which the desired patterns are formed is often used as anoriginal in the so-called photoetching process. More specifically, aphotopolymer-containing layer is exposed via the photomask in a statethat the photomask is kept in close contact with the layer orsuperimposed on the layer with a slight gap between them, thendeveloped, and further dried. Thus, patterns corresponding to thepatterns in the photomask are formed in the photopolymer-containinglayer.

Incidentally, the emulsion layer used for a photomask contains gelatinas a main component, and the pencil hardness thereof is 2B or below.Therefore, when the contact exposure in a photoetching process iscarried out in a condition that the emulsion layer surface is broughtinto close contact with the photopolymer layer as a subject withoutproviding any special protective layer, the photomask tends to receiveflaws on the surface to result in a partial loss of its pattern data.Further, the emulsion layer surface is contaminated with microbes tocause a loss of information on the photomask or defective shooting.

Under these circumstances, the aforementioned defects have so far beencompensated for by bonding a commercial pressure sensitiveadhesive-applied film to the emulsion surface of an unprotectedphotomask (the term “an unprotected photomask” as used herein means aphotomask which is provided with no protective layer or the like but hasan emulsion layer surface in a bare state). However, such a pressuresensitive adhesive-applied film has a drawback of being sensitive toscratches of hard foreign materials because the layer of the pressuresensitive adhesive is soft and the film itself tends to sufferscratches. Therefore, increase in the number of times such a photomaskhas been used necessitates replacing the protective layer of thephotomask by a new one. Therefore, it cannot be said that commercialpressure sensitive adhesive-applied films function satisfactorily asprotective layers.

When the pressure sensitive adhesive-applied films are increased in filmthickness for diminishing the foregoing drawback, the protective layerstrength is heightened, but the UV-ray transmittance as a photomask'soptical characteristic is lowered. As a result, it becomes necessary toextend the exposure time, and what is worse, high-definition patterningbecomes impossible because reflection, refraction and scattering oflight reveal their influences. In other words, in the case of usingpressure sensitive adhesive-applied films, the photomask's drawback ofbeing sensitive to flaws cannot be overcome by adjustment of filmthickness since the film thickness decreased to an extent that noproblems are caused in the foregoing aspect of optical characteristicscannot secure the strength as the protective layer (the order of B inpencil hardness). In addition, such thin films tend to become wrinkledat the time when they are bonded to unprotected photomasks, so theycause lowering of workability. Accordingly, the pressure sensitiveadhesive-applied films can hardly satisfy all the requirements,sufficient protective layer strength, satisfactory UV-ray transmittanceand good workability.

Furthermore, as described in Japanese Patent Laid-Open No. Hei11-305420, it has been tried to provide protective layers by applyingcoating materials on unprotected photomasks according to a variety ofmethods, such as spray coating, spin coating and dip coating methods,and then thermally curing them simultaneously with drying. However, suchmethods require a heat-applied aging time of 18 to 72 hours, so there isthe fear of a damage to the emulsion surfaces. In addition, it is hardto control the coating layer thickness in the foregoing coatingprocesses (wet processes), so it has been difficult to put such methodsto practical use.

Therefore, a first object of the present invention is to provide atransfer sheet which enables easy formation of a protective layer havinggood contact with an emulsion layer and high resistance to scratching,even when the emulsion surface is poor in heat resistance and solventresistance.

A second object of the present invention is to provide a protectivelayer-attached photomask having excellent optical characteristics andhigh resistance to scratching.

DISCLOSURE OF THE INVENTION

The inventors have found that a transfer sheet having excellent transferworkability can be obtained by providing a specially designed adhesiveuncured layer for photographic emulsion surface protection use (thislayer is referred to as “an adhesive layer” hereinafter) on one side ofa support. More specifically, an embodiment of the invention is atransfer sheet for forming a photographic emulsion surface protectivelayer, with the transfer sheet having an adhesive layer containing atleast an ionized radiation-curable resin composition on a supportsurface having releasability, wherein the ionized radiation-curableresin composition comprises a hydrophilic group-containingmonofunctional (meth)acrylate and a polyfunctional (meth)acrylate.Another embodiment of the invention is a method of forming aphotographic emulsion surface protective layer by use of the aforesaidtransfer sheet. Still another embodiment of the invention is a photomaskhaving a protective layer formed by using the foregoing method. In theseembodiments, a cure layer may be present between the support and theadhesive layer.

In particular, further incorporation of a thermosetting resin and/orpolyamine into the adhesive layer of the present transfer sheet makesadhesion control easy and has an advantage in that the protective layerformed can have high adhesion to the emulsion surface of a photomask andhigh strength. The thus obtained protective layer-attached photomaskbear comparison with the protective layer-free photomask in point ofoptical characteristics, and besides, it is remarkably improved inresistance to scratching.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural view showing an embodiment of the presenttransfer sheet, and FIG. 2 is a schematic diagram showing an embodimentof the transfer process for providing a protective layer on a photomaskby use of the present transfer sheet.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is described below in detail.

The support having releasability which is used for the present transfersheet can be selected appropriately from known materials as far as thematerials are releasable from an adhesive layer or a cure layer providedthereon. Examples of a support especially suitable for the presenttransfer sheet include plastic films containing as a main componentpolyethylene terephthalate, polypropylene, polyvinyl chloride,polystyrene, polycarbonate, or triacetate. The support used has noparticular restriction as to the thickness, but the thickness rangingfrom about 20 μm to about 150 μm is advantageous in that wrinkles andbubbles are hardly formed at the time of transfer to a subject ofprotection, so good workability can be obtained.

In the invention, a release agent-treated substrate prepared by treatinga sheet-form substrate with a release agent may also be used as thesupport for the purpose of effecting easy transfer of an adhesive layer.As examples of such a release agent-treated substrate, mention may bemade of not only commercially available release films provided withcoatings of silicone, Teflon or the like, but also sheet-form substrateshaving thereon release layers which are each formed by coating a coatingcomposition containing urethane resin, melamine resin, fluorocarbonresin, silicone resin, polyester resin, polyolefin resin or a mixturethereof so as to have a dry thickness of 0.1 to 5 μm, preferably 1 to 2μm, and then drying the composition coated.

When the release layer is rendered matte by adding a pigment thereto,the matte pattern is formed on an adhesive layer provided thereon, or acure layer provided thereon when required; as a result, it becomespossible to lay a protective layer having a matte outermost layer on asubject to protect. In other words, the outermost layer of theprotective layer transferred from the present transfer sheet can havethe same surface profile as that of the release surface of the transfersheet support. When the release surface of the support is smooth, theoutermost surface of the protective layer transferred becomes clear;while, when the release surface is matte, the outermost surface of theprotective layer transferred becomes matte. The matte release layer canbe obtained with ease by adding the foregoing filler in an amount of atleast 0.5 parts by weight to 100 parts by weight of resin.

Even when the outermost layer is rendered matte, no pigment is presentinside the protective layer. As a result, the protective layer causes noscattering of light in its interior, and so it makes it possible toreproduce fine patterns and can used to advantage as the protectivelayer of a photomask. In the case of forming patterns in a photoresiston a printed wiring board, for instance, a photomask is brought intosufficiently close contact with the surface of the photoresist on aprinted wiring board under a reduced pressure, and then subjected toexposure. In this case, the air in the gap between the photomask and thephotoresist can be evacuated smoothly on condition that the protectivelayer of the photomask is made matte, so air bubbles remaining betweenthem can be prevented from evolving. The remaining air bubbles becomecauses of refraction, reflection and scattering of light upon exposurefor patterning and interfere with reproduction of patterns.

In the case of performing exposures in a condition that a slightdistance is kept between a photomask and a subject (a light-sensitivematerial), or the so-called proximity exposures, it is appropriate thatthe photomask surface on the side of the light-sensitive material besmooth. This is because a rough photomask surface causes a problem thatultraviolet rays used for exposure refract on the photomask surface tomake the light-sensitive material surface uneven. When the presentphotomask is used for patterning with a precision of a pattern width of50 μm or below by performing proximity exposures in particular, it isdesirable that the surface roughness of the support be 5.0×10⁻² μm orbelow in terms of ten-point mean roughness with respect to a referencelength of 0.8 mm defined in JIS-B-0601. When the surface roughness isgreater than 5.0×10⁻² μm, asperities are developed on the dry filmpatterns (sensitive material surface) after exposure to cause problems.

In the invention, the adhesive layer is cured by irradiation withionized radiation before release of the support. Therefore, it isdesirable for the support to have a high ionized-radiationtransmittance. Specifically, the suitable ionized-radiationtransmittance of the support is at least 50%, preferably at least 80%.

In order that the present protective layer after curing can havesufficient resistance to scratching, satisfactory solvent-proofingproperties and close adhesion to a photographic emulsion surface, it isappropriate that the uncured protective layer for photographic emulsionsurface protection use have a curing index (I) represented by thefollowing equation in the range of 80 to 300, preferably 110 to 300:I=R 1×S 1+R 2×S 2+ . . . +Rn×Snwherein I is a curing index; R1, R2, . . . , Rn are percentages byweight of resin components (resin 1, resin 2, . . . , resin n),respectively, in the uncured protective layer; and S1, S2, . . . , Snare acryloyl group numbers of resin components (resin 1, resin 2, . . ., resin n), respectively, in the uncured protective layer.

The term “ionized radiation” as used in the invention is intended toinclude electromagnetic waves of any kinds as far as they havecapabilities of causing ionization in materials. However, industriallyutilizable electromagnetic waves are ultraviolet rays and electronbeams. Additionally, γ-rays and the like are also usable. From thepractical point of view, ultraviolet rays are preferred, and thesuitable sources therefor include a high-pressure mercury lamp, anultrahigh-pressure mercury lamp, a metal halide lamp and so on.

The term “an ionized radiation curable resin composition” as used in theinvention means a composition which can be cured by irradiation withionized radiation. In the composition are specifically used oligomersand/or monomers containing acryloyl or methacryloyl groups as functionalgroups, such as acrylates, methacrylates and so on. More specifically,urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate,(meth)acrylates of silicone type and the like are used in the form ofoligomer and/or monomer.

In the invention, a hydrophilic group-containing monofunctional(meth)acrylate monomer is selected from those resins, and incorporatedas an essential component in an ionized radiation curable resincomposition together with a polyfunctional (meth)acrylate describedhereinafter. By incorporation of a hydrophilic group-containingmonofunctional (meth)acrylate monomer, elasticity can be imparted to theprotective layer and markedly improved contact with the photomaskemulsion surface can be achieved. In addition, the hydrophilic groupcontained in the monomer produces an effect of lowering surfaceresistance of the protective layer, so anti-static properties are alsoimparted thereby. The photomask surface prevented from being electrifiedoffers an advantage in that adhesion of foreign substances, such as dustand the like, is prevented. It is appropriate that the hydrophilicgroup-containing monofunctional (meth)acrylate be contained in aproportion of 20 to 55 weight %, particularly 25 to 50 weight %, on asolids basis in an adhesive uncured protective layer.

Polyfunctional (meth)acrylates in the ionized radiation curable resincomposition act so as to heighten the surface strength of the protectivelayer and impart solvent-proof properties to the protective layer.However, when the polyfunctional (meth)acrylate resin used has a highviscosity, the compliance of the adhesive layer with stepped patterns onthe photomask emulsion surface becomes poor. As a result, air bubblestend to be trapped in the bonded region. From the viewpoint ofpreventing contamination with air bubbles, it is desirable to selectlow-viscosity polyfunctional (meth)acrylate resins, specifically resinshaving a viscosity of 1,000 (cps at 25° C.) or below as measured with aBrookfield type viscometer.

In general the ionized radiation curable resins have fluidity in anuncured state, and so they suffer a problem of having a tendency to besqueezed out of the edges of a transfer sheet when the transfer sheet iswound up. In the invention, therefore, it is preferable to adjust thehardness of the adhesive layer to the values required by mixing anappropriate amount of at least one thermosetting or heat-reactive resinwith the present ionized radiation curable resins, and thermally curingthe resulting composition. Further, the adhesive layer can havestickiness on such a level as to enable tentative adhesion to asubstrate by addition of such a thermosetting resin.

The thermosetting resins usable in the invention are resins capable ofbeing cured by heating, with examples including urea resin, melamineresin, phenol resin, epoxy resin, alkyd resin, urethane resin and thelike.

Instead of these resins or together with these resins, at least oneresin capable of reacting with ionized radiation curable resins underheating can be used in the invention. The use of such a reactive resinis beneficial, because it can increase the strength of the adhesivelayer after curing.

Of the resins capable of reacting with ionized radiation curable resinsunder heating, the resins most suitably used in the invention are resinscapable of being cured by addition reaction of active hydrogen atoms(e.g., hydrogen atoms of active amines) to acrylic unsaturated bonds. Asexamples of these resins, mention may be made of polyamines containingprimary or secondary amino groups. Addition of at least one polyamineselected from polyamines containing primary or secondary amino groups toionized radiation curable resins having acrylic unsaturated bonds (towhich monomers or oligomers may be added) causes Michael additionreaction to yield stickiness. From the viewpoint of stickinessadjustment, it is advantageous in particular that the foregoingpolyamines are acrylic graft copolymers which each have an acrylic trunkchain and acrylamide side chains (comb polymers). These acrylic graftcopolymers are also effective for prevention of electrification.

The aforementioned thermosetting resins and resins capable of reactingwith ionized radiation curable resins may be used independently of eachother or in various combinations thereof.

In the invention, it is preferable in point of cost that thethermosetting resins or the ionized radiation curable resins be cured byheat for drying the coating composition coated for forming an adhesivelayer. Therefore, it is undesirable to use resins having reactiontemperatures higher than the softening point of a support, so it isappropriate that the resins commencing the reaction at temperatures ofabout 60° C. to about 130° C. be selected.

In the invention, the adhesive layer has stickiness, so a separator canbe provided, if needed. In forming the present transfer sheet intowinding products, it is beneficial in point of working efficiency tosubject the support to release treatment on the side opposite to theadhesive layer-provided side, or to laminate a release-treated film(separator) on the adhesive layer after drying.

Examples of a separator which can be used therein include films ofplastics, such as polyethylene terephthalate, polyethylene,polypropylene and the like, and paper or like sheets coated with arelease agent, such as a silicone or the like. The separators 4 to 200μm in thickness can be used, but from the viewpoint of workability it isappropriate that their thicknesses be from 12 to 50 μm. Of course, sucha separator is removed at the time when the present transfer sheet isbonded to a subject of protection.

In using the present transfer sheet, the adhesive layer is bonded to theemulsion surface, and then irradiated with ionized radiation via thesupport or after removal of the support therefrom. In the case offaithfully copying the surface profile of the support to the protectivelayer, the irradiation via the support is preferred. The adhesive layeris cured by irradiation with ionized radiation to get sufficientadhesion to the emulsion surface. The irradiation dose required forcomplete adhesion of the adhesive layer to the surface of a photographicemulsion as a subject can be adjusted properly depending on the type ofa photopolymerization initiator used, the resin composition used for theadhesive layer, and so on. Specifically, the suitable irradiation doseis from 30 to 1,000 mJ. Preferably, it is not lower than 100 mJ in thecase where the ease of storage and handling are concerned; while it isnot higher than 500 mJ from the viewpoint of reduction in curing time.

In the invention, the layer transferred to a subject may be constitutedof two or more layers. The transfer layer is required to have twocharacteristics, (1) development of hardness and (2) adhesion to asubject. Basically, the former characteristic is a requirement for allthe constituent layers, and the latter is a requirement for the surfacebrought into contact with the subject. In general, an increase inadhesion strength of a transfer layer to a subject causes a decrease inhardness of the transfer layer. When the conditions incompatible witheach other need to be satisfied, it is required that the transfer layerbe constituted of two optimized layers. With respect to the transferlayer constituted of at least two layers as mentioned above, the curelayer becomes the outermost layer after transfer, so the adhesion to asubject may receive no consideration. On the other hand, it is requiredto design the layer on the side brought into contact with a subject (theadhesive layer) in consideration of adhesion to a substrate. As resinsused in the cure layer, resins similar in type to the resins used in theadhesive layer are preferred, because close adhesion between theselayers can be attained.

When the adhesive layer is provided after forming a cure layer on asupport in the invention, it is preferable to cure the cure layer beforeproviding the adhesive layer, because the coating suitability of theadhesive layer can be enhanced.

When the total thickness of the layers transferred to a subject is toothick, there is the fear of cracking at the time of transfer; while,when the total thickness is too thin, the cure layer cannot perform itsfunction. Therefore, the suitable total thickness of layers transferredis from 1 to 15 μm, particularly from 1 to 8 μm. When the transfer layeris constituted of the cure layer and the adhesive layer, the suitablethickness of the cure layer is from 1 to 5 μm and that of the adhesivelayer is from 3 to 10 μm.

Although a pigment, such as silica, colloidal silica, mica, titaniumdioxide, alumina, calcium carbonate, aluminum hydroxide or the like, canbe added to the adhesive layer, the pigment added becomes a cause oflight scattering. As a result, the use of a pigment in a large amountmakes it impossible to keep optical characteristics of the photomask ina satisfactory condition. Therefore, it is required to control theamount of a pigment added to 5 parts by weight or below per 100 parts byweight of the foregoing resins, and it is preferable for the adhesivelayer to be free of pigments.

The cure layer and the adhesive layer of the present transfer sheet cancontain additives, such as a polymerization initiator, a leveling agent,an antiseptic, a coloring agent, an ultraviolet absorbent, anantioxidant, a plasticizer and so on, in such amounts as not to impairthe present effects.

In addition, the release layer, the cure layer and the adhesive layer toconstitute the present transfer sheet can be formed as appropriate byuse of a coating machine selected properly from known coaters includinga bar coater, a roll coater, a kiss coater, a curtain coater, a diecoater, a blade coater, a comma coater and so on. In this case, thecoating compositions coated on the support are each dried with a knowndryer, such as an air floating dryer or an infrared dryer.

In providing the cure layer, the adhesive layer and the release layerfor the support in the invention, it is a matter of course that such aplurality of layers may be provided by use of a single piece ofcontinuous coating equipment (including a drying unit also).

In transferring the present transfer sheet to a subject surface(emulsion surface), the sheet is tentatively bonded to the subjectsurface by adhesion of the adhesive layer, and then completely bondedthereto by irradiation with ionized radiation. Accordingly, the transferoperation can be easily performed without heating or application of asolvent or so on. Further, since each of the curing and adhesive layerscontains both hydrophilic group-containing monofunctional (meth)acrylateand low-viscosity ionized radiation curable resin made up ofpolyfunctional (meth)acrylate units, the present transfer sheet canprovide a protective layer excellent in resistance to scratching, closeadhesion to the emulsion surface and solvent-proof properties.

In particular, the present transfer sheet is effective in providing aprotective layer for protecting the emulsion surface of a photomask.Further, the photomask provided with the present protective layer by theuse of the present transfer sheet can be used consistently for a longtime, because the protective layer provided has not only excellentoptical characteristics (reduced refraction and reflection of light fromthe interface surface) but also high resistance to scratching and closeadhesion to the emulsion surface.

EXAMPLES

In order to illustrate the present invention in more detail, thefollowing examples are presented. However, the invention should not beconstrued as being limited to these examples. Additionally, all “parts”in Examples are by weight.

Example 1

(1) Preparation of Support:

On one side of a biaxially stretched 50 μm-thick polyethyleneterephthalate (abbreviated as “PET” hereinafter) film, the followingrelease layer forming solution was coated by means of a roll coater, anddried for 1 minute at 130° C. Thus, a release layer having a thicknessof 2 μm was formed.

<Release Layer Forming Solution>

-   -   (a) Acrylamide copolymer (Tesfine 322, trade name, a product of        Hitachi Kasei Polymer Co., Ltd.): 1.8 parts    -   (b) Epoxy-melamine copolymer (SP-DRC No. 153N, trade name, a        product of Dainippon Ink and Chemicals, Inc.): 41 parts    -   (c) Paratoluenesulfonic acid (Dryer 900, trade name, a product        of Hitachi Kasei Polymer Co., Ltd.): 0.2 parts

(d) Solvent: ethyl acetate 46 parts methyl ethyl ketone 11 parts(2) Preparation of Photographic Emulsion Surface Protective Layer inUncured State:

On the release layer of the support prepared in (1), the followingsolution for forming a photographic emulsion surface protective layer inan uncured state was coated by means of a roll coater, and dried for 1minute at 100° C. Thus, a 6 μm-thick uncured layer for protecting aphotographic emulsion surface was formed.

<Solution for Forming Photographic Emulsion Surface Protective Layer>

(Ionized Radiation Curable Resin Composition)

A transfer sheet was prepared in the same manner as in Example 1, exceptthat the solution for forming the photographic emulsion surfaceprotective layer in an uncured state was replaced by the followingsolution. The curing index of the thus formed photographic emulsionsurface protective layer in the uncured state was 150.

<Solution for Forming Photographic Emulsion Surface Protective Layer>

(Ionized Radiation Curable Resin Composition)

(3) Preparation of Transfer Sheet:

On the surface of this photographic emulsion surface protective layer inan uncured state, a 25 μm-thick PET film coated with silicone on oneside was laminated as a separator to prepare a transfer sheet. Thecuring index of the photographic emulsion surface protective layer in anuncured state was 254.

(4) Preparation of Protective Layer-Covered Photomask:

The separator of the transfer sheet prepared in the foregoing manner waspeeled away, and the transfer sheet and each of photomasks having astheir substrates a plastic film and glass, respectively, were bondedtogether by means of a laminator. In both cases, the lamination waseasily performed without becoming wrinkled. Each of these laminates wasexposed from the PET film side by means of a high-pressure mercury lampso that the integrated amount of exposure at 365 nm reached 450 mj/cm²,and then the support was peeled away from the transfer sheet. Thus, aprotective layer was formed on each of the photomasks.

The protective layer formed on each photomask had a hard surface,excellent resistance to scratches, and satisfactory adhesion to theemulsion surface. Further, it had excellent optical characteristics andhigh resistance to chemicals.

Example 2

A transfer sheet was prepared in the same manner as in Example 1, exceptthat the solution for forming the photographic emulsion surfaceprotective layer in an uncured state was replaced by the followingsolution. The curing index of the thus formed photographic emulsionsurface protective layer in the uncured state was 150.

<Solution for Forming Photographic Emulsion Surface Protective Layer>

(Ionized Radiation Curable Resin Composition)

-   -   (a) Trifunctional acrylate (Aronix M-309, trade name, a product        of Toagosei Chemical Industry Co., Ltd.): 12 parts    -   (b) COOH group-containing monofunctional acrylate (Aronix        M-5400, trade name, a product of Toagosei Chemical Industry Co.,        Ltd.): 9 parts    -   (c) Polyamine (an acrylic graft copolymer, L-40M, trade name, a        product of Soken Chemical & Engineering Co., Ltd.): 9 parts    -   (d) Reaction initiator (Lucirin TPO, trade name, a product of        BASF Japan Ltd.): 0.1 parts

(e) Diluent: ethyl acetate 17.2 parts methyl ethyl ketone 17.2 partsethyl cellosolve 8.5 parts

By the use of the transfer sheet thus obtained, protective layer-coveredPhotomasks were prepared in the same manner as in Example 1. Theprotective layer formed on each of the photomasks was excellent insurface hardness, close adhesion, optical characteristics and chemicalresistance.

Example 3

A transfer sheet and protective layer-covered photomasks were preparedin the same manners as in Example 1, except that the solution forforming the photographic emulsion surface protective layer in an uncuredstate was replaced by the following solution. The curing index of thethus formed photographic emulsion surface protective layer in theuncured state was 130.

<Solution for Forming Photographic Emulsion Surface Protective Layer>

(Ionized Radiation Curable Resin Composition)

-   -   (a) Trifunctional acrylate (Aronix M-309, trade name, a product        of Toagosei Chemical Industry Co., Ltd.): 9 parts    -   (b) COOH group-containing monofunctional acrylate (Aronix        M-5400, trade name, a product of Toagosei Chemical Industry Co.,        Ltd.): 12 parts    -   (c) Polyamine (an acrylic comb copolymer, L-40M, trade name, a        product of Soken Chemical & Engineering Co., Ltd.): 9 parts    -   (d) Reaction initiator (Lucirin TPO, trade name, a product of        BASF Japan Ltd.): 0.1 parts

(e) Diluent: ethyl acetate 17.2 parts methyl ethyl ketone 17.2 partsethyl cellosolve 8.5 parts

By the use of the transfer sheet thus obtained, protective layer-coveredPhotomasks were prepared in the same manner as in Example 1. Theprotective layer formed on each of the photomasks was excellent insurface hardness, close adhesion, optical characteristics and chemicalresistance.

Example 4

A transfer sheet and protective layer-covered photomasks were preparedin the same manners as in Example 1, except that the solution forforming the photographic emulsion surface protective layer in an uncuredstate was replaced by the following solution. The curing index of thethus formed photographic emulsion surface protective layer in theuncured state was 140.

<Solution for Forming Photographic Emulsion Surface Protective Layer>

(Ionized Radiation Curable Resin Composition)

-   -   (a) Polyfunctional acrylate (Sanrad H-601, trade name, a product        of Sanyo Chemical Industsries, Ltd.): 9 parts    -   (b) COOH group-containing monofunctional acrylate (Aronix        M-5400, trade name, a product of Toagosei Chemical Industry Co.,        Ltd.): 15 parts    -   (c) Thermosetting resin (mixture of 3 parts of acrylpolyol,        Thermolac 2000, trade name, a product of Soken Chemical &        Engineering Co., Ltd., with 3 parts of polyisocyanate, Takenate        D110N, trade name, a product of Takeda Chemical Industries,        Ltd.)    -   (d) Reaction initiator (Lucirin TPO, trade name, a product of        BASF Japan Ltd.): 0.1 parts

(e) Diluent: ethyl acetate 26.4 parts methyl ethyl ketone 26.4 partsethyl cellosolve 13.1 parts

By the use of the transfer sheet thus obtained, protective layer-coveredPhotomasks were prepared in the same manner as in Example 1. Theprotective layer formed on each of the photomasks was excellent insurface hardness, close adhesion, optical characteristics and chemicalresistance.

Example 5

On the same support as used in Example 1, the cure layer formingsolution described below was coated by means of a roll coater, dried for1 minute at 100° C., and then exposed with a high-pressure mercury lampso that the integrated amount of exposure (at 365 nm) reached 300mj/cm². Thus, a cure layer having a thickness of about 1 μm was formed.

<Cure Layer Forming Solution>

(Ionized Radiation Curable Resin Composition)

-   -   (a) Polyfunctional acrylate (Sanrad H-601, trade name, a product        of Sanyo Chemical Industries, Ltd.): 7 parts    -   (b) COOH group-containing monofunctional acrylate (Aronix        M-5400, trade name, a product of Toagosei Chemical Industry Co.,        Ltd.): 4 parts    -   (c) Polyamine (acrylic comb polymer, L-40M, trade name, a        product of Soken Chemical & Engineering Co., Ltd.): 4.5 parts    -   (d) Reaction initiator (Lucirin TPO, trade name, a product of        BASF Japan Ltd.): 0.1 parts

(e) Diluent: ethyl acetate 28.4 parts methyl ethyl ketone 28.4 partsethyl cellosolve 14.1 parts

On this cure layer, the following solution for forming a photographicemulsion surface protective layer was further coated by means of a rollcoated, and dried for 1 minute at 100° C. Thus, a 6 μm-thick uncuredlayer for protecting a photographic emulsion surface was formed. And thecuring index of the thus formed photographic emulsion surface protectivelayer in an uncured state was 194.

<Solution for Forming Photographic Emulsion Surface Protective Layer>

(Ionized Radiation Curable Resin Composition)

-   -   (a) Polyfunctional acrylate (Sanrad H-601, trade name, a product        of Sanyo Chemicals Co., Ltd.): 8 parts    -   (b) COOH group-containing monofunctional acrylate (Aronix        M-5400, trade name, a product of Toagosei Chemical Industry Co.,        Ltd.): 13 parts    -   (c) Polyamine (acrylic graft copolymer, L-40M, trade name, a        product of Soken Chemical & Engineering Co., Ltd.): 9 parts    -   (d) Reaction initiator (Lucirin TPO, trade name, a product of        BASF Japan Ltd.): 0.1 parts

(e) Diluent: ethyl acetate 17.2 parts methyl ethyl ketone 17.2 partsethyl cellosolve 8.5 parts

Then, on the surface of this photographic emulsion surface protectivelayer in an uncured state, a 25 μm-thick PET film coated with siliconeon one side was laminated as a separator to prepare a transfer sheet.

By the use of the thus prepared transfer sheet, protective layer-coveredPhotomasks were prepared in the same manner as in Example 1. Theprotective layer formed on each of the photomasks was excellent insurface hardness, close adhesion, optical characteristics and chemicalresistance.

Example 6

A transfer sheet and protective layer-covered photomasks were preparedin the same manners as in Example 1, except that the solution forforming the photographic emulsion surface protective layer in an uncuredstate was replaced by the following solution. The curing index of thethus formed photographic emulsion surface protective layer in theuncured state was 282.

<Solution for Forming Photographic Emulsion Surface Protective Layer>

(Ionized Radiation Curable Resin Composition)

-   -   (a) Polyfunctional acrylate (Sanrad H-601, trade name, a        UV-curable resin produced by Sanyo Chemical Industries, Ltd.,        wherein the monomer having an acryloyl group number of 5 and the        monomer having an acryloyl group number of 6 are mixed in        proportions of 4:6): 13.5 parts    -   (b) COOH group-containing monofunctional acrylate (Aronix        M-5400, trade name, a product of Toagosei Chemical Industry Co.,        Ltd.): 9 parts    -   (c) Polyamine (an acrylic graft copolymer having an acrylic        trunk chain and N-methylol acrylamide side chains, L-40M, trade        name, a product of Soken Chemical & Engineering Co., Ltd.): 7.5        parts    -   (d) Reaction initiator (Lucirin TPO, trade name, a product of        BASF Japan Ltd.): 0.1 parts

(e) Diluent: ethyl acetate 19 parts methyl ethyl ketone 19 parts ethylcellosolve 9.4 parts

By the use of the transfer sheet thus obtained, protective layer-coveredPhotomasks were prepared in the same manner as in Example 1. Theprotective layer formed on each of the photomasks was excellent insurface hardness, close adhesion, optical characteristics and chemicalresistance.

Example 7

A transfer sheet and protective layer-covered photomasks were preparedin the same manners as in Example 1, except that the solution forforming the photographic emulsion surface protective layer in an uncuredstate was replaced by the following solution. The curing index of thethus formed photographic emulsion surface protective layer in theuncured state was 226.

<Solution for Forming Photographic Emulsion Surface Protective Layer>

(Ionized Radiation Curable Resin Composition)

-   -   (a) Polyfunctional acrylate (Sanrad H-601, trade name, a        UV-curable resin produced by Sanyo Chemical Industries, Ltd.,        wherein the monomer having an acryloyl group number of 5 and the        monomer having an acryloyl group number of 6 are mixed in        proportions of 4:6): 10.5 parts    -   (b) COOH group-containing monofunctional acrylate (Aronix        M-5400, trade name, a product of Toagosei Chemical Industry Co.,        Ltd.): 9 parts    -   (c) Polyamine (an acrylic graft copolymer having an acrylic        trunk chain and N-methylol acrylamide side chains, L-40M, trade        name, a product of Soken Chemical & Engineering Co., Ltd.): 10.5        parts    -   (d) Reaction initiator (Lucirin TPO, trade name, a product of        BASF Japan Ltd.): 0.1 parts

(e) Diluent: ethyl acetate 15.4 parts methyl ethyl ketone 15.4 partsethyl cellosolve 7.6 parts

By the use of the transfer sheet thus obtained, protective layer-coveredPhotomasks were prepared in the same manner as in Example 1. Theprotective layer formed on each of the photomasks was excellent insurface hardness, close adhesion, optical characteristics and chemicalresistance.

Example 8

A transfer sheet and protective layer-covered photomasks were preparedin the same manners as in Example 1, except that the solution forforming the photographic emulsion surface protective layer in an uncuredstate was replaced by the following solution. The curing index of thethus formed photographic emulsion surface protective layer in theuncured state was 272.

<Solution for Forming Photographic Emulsion Surface Protective Layer>

(Ionized Radiation Curable Resin Composition)

-   -   (a) Bifunctional acrylate (NK-Ester APG-200, trade name, a        product of Shin-Nakamura Chemical Co., Ltd.): 6 parts    -   (b) COOH group-containing monofunctional acrylate (Aronix        M-5400, trade name, a product of Toagosei Chemical Industry Co.,        Ltd.): 12 parts    -   (c) Polyamine (an acrylic graft copolymer having an acrylic        trunk chain and N-methylol acrylamide side chains, L-40M, trade        name, a product of Soken Chemical & Engineering Co., Ltd.): 12        parts    -   (d) Reaction initiator (Lucirin TPO, trade name, a product of        BASF Japan Ltd.): 0.1 parts

(e) Diluent: ethyl acetate 13.6 parts methyl ethyl ketone 13.6 partsethyl cellosolve 6.7 parts

By the use of the transfer sheet thus obtained, protective layer-coveredPhotomasks were prepared in the same manner as in Example 1. Theprotective layer formed on each of the photomasks was excellent insurface hardness, close adhesion and optical characteristics, and hadpractically sufficient chemical resistance.

Comparative Example 1

On one side of a 6 μm-thick transparent PET film, the following releaselayer forming solution was coated by means of a roll coater, dried for 3minutes at 80° C., and further underwent aging treatment at 40° C. for48 hours. Thus, a release layer having a thickness of about 1 μm wasformed. Next the following adhesive layer forming solution was coated onthe other side of the PET film by means of a roll coater, and dried for2 minutes at 80° C., thereby forming an adhesive layer having athickness of about 3 μm.

<Release Layer Forming Solution>

-   -   (a) Silicone-modified acrylic resin (SG-540SA, trade name, a        product of Teikoku Chemical Industries Co., Ltd.): 3 parts    -   (b) Acrylpolyol (Thermolac S2000, trade name, a product of Soken        Chemical & Engineering Co., Ltd.): 17 parts    -   (c) Isocyanate (Takenate D-110N, trade name, a product of Takeda        Chemical Industries, Ltd.): 8 parts    -   (d) Toluene: 36 parts        -   Methyl ethyl ketone: 36 parts            <Adhesive Layer Forming Solution>    -   (a) Acrylpolyol (SK-dyne, trade name, a product of Soken        Chemical & Engineering Co., Ltd.): 100 parts    -   (b) Isocyanate (TD-75, trade name, a product of Soken Chemical &        Engineering Co., Ltd.): 0.2 parts    -   (c) Ethyl acetate: 2 parts

On the surface of the adhesive layer thus formed, a 25 μm-thick PET filmcoated with silicone on one side was laminated as a separator to preparea surface protective film.

The separator of the surface protective film prepared in the foregoingmanner was peeled away, and the protective film was bonded to each of afilm photomask and a glass photomask by means of a laminator. In thislamination process, the protective film was likely to have wrinkles andbad in workability. In addition, the protective film on each photomask,though it had satisfactory optical characteristics, had low resistanceto scratches. Specifically, it had a pencil scratch value of B whenmeasured on a glass plate.

Comparative Example 2

A transfer sheet was prepared in the same manner as in Example 1, exceptthat the solution for forming the photographic emulsion surfaceprotective layer in an uncured state was replaced by the followingsolution. The curing index of the thus formed photographic emulsionsurface protective layer in the uncured state was 392.

<Solution for Forming Photographic Emulsion Surface Protective Layer>

(Ionized Radiation Curable Resin Composition)

-   -   (a) Polyfunctional acrylate (a UV-curable resin wherein the        monomer having an acryloyl group number of 5 and the monomer        having an acryloyl group number of 6 are mixed in proportions of        4:6, Sanrad H-601, trade name, a product of Sanyo Chemical        Industries, Ltd.,): 21 parts    -   (b) Polyamine (an acrylic graft copolymer, L-40M, trade name, a        product of Soken Chemical & Engineering Co., Ltd.): 9 parts

(c) Diluent: ethyl acetate 17.2 parts methyl ethyl ketone 17.2 partsethyl cellosolve 8.5 parts

By the use of the transfer sheet thus obtained, protective layer-coveredPhotomasks were prepared in the same manner as in Example 1. Theprotective layer formed on each photomask was very poor in adhesion tothe photomask's emulsion surface.

Comparative Example 3

A transfer sheet was prepared in the same manner as in Example 1, exceptthat the solution for forming the photographic emulsion surfaceprotective layer in an uncured state was replaced by the followingsolution. The curing index of the thus formed photographic emulsionsurface protective layer in the uncured state was 254.

<Solution for Forming Photographic Emulsion Surface Protective Layer>

(Ionized Radiation Curable Resin Composition)

-   -   (a) Polyfunctional acrylate (a UV-curable resin wherein the        monomer having an acryloyl group number of 5 and the monomer        having an acryloyl group number of 6 are mixed in proportions of        4:6, Sanrad H-601, trade name, a product of Sanyo Chemical        Industries, Ltd.): 12 parts    -   (b) Monofunctional acrylate (Aronix M-120, trade name, a product        of Toagosei Chemical Industry Co., Ltd.): 9 parts    -   (c) Polyamine (an acrylic graft copolymer having an acrylic        trunk chain and N-methylol acrylamide side chains, L-40M, trade        name, a product of Soken Chemical & Engineering Co., Ltd.): 9        parts    -   (d) Reaction initiator (Lucirin TPO, trade name, a product of        BASF Japan Ltd.): 0.1 parts

(e) Diluent: ethyl acetate 17.2 parts methyl ethyl ketone 17.2 partsethyl cellosolve  8.5 parts

By the use of the transfer sheet thus obtained, protective layer-coveredPhotomasks were prepared in the same manner as in Example 1. Theprotective layer formed on each photomask was poor in adhesion to thephotomask's emulsion surface.

The results obtained in Examples and Comparative Examples are summarizedin Tables 1 and 2.

TABLE 1 Protective Layer in Uncured State Polyfunctional monomer/monofunctional monomer/thermosetting Curing resin (or polyamine) IndexExample 1 40/30/30 254 Example 2 40/30/30 150 Example 3 30/40/30 130Example 4 30/50/20 218 Example 5 27/43/30 194 Example 6 45/30/25 282Example 7 35/30/35 226 Example 8 40/30/30 254 Comparative — — Example 1Comparative  70/0/30 392 Example 2 Comparative 40/30 (free ofhydrophilic group)/30 254 Example 3

TABLE 2 Close Chemical Pencil Adhesion Transmittance resistance hardness(%) (%) (times) Example 1 2H 100 88 >100 Example 2 2H 100 88 >100Example 3 2H 100 87 >100 Example 4 H 85 87 >100 Example 5 2H 100 87 >100Example 6 2H 100 87 >100 Example 7 2H 100 87 >100 Example 8 H 100 87 50Comparative B 100 85 >100 Example 1 Comparative HB 0 88 >100 Example 2Comparative HB 0 87 >100 Example 3(Evaluation Methods)

-   -   Pencil Hardness: A protective layer-covered photomask was placed        on a glass plate, and the hardness of the cured layer thereof        was evaluated by a pencil scratch test (according to JIS K        5400). And the pencil scratch value was determined.    -   Close adhesion: Close adhesion between the emulsion surface and        a protective layer was evaluated by a crosshatch test (according        to JIS K 5400).    -   Transmittance: A cured layer and a protective film were formed        on a blue sheet glass (2 mm in thickness), and examined for        transmittance at 365 nm by means of a spectrophotometer (Hitachi        Spectrophotometer U-3310), wherein the blue sheet glass in        itself had the transmittance of 89% at 365 nm.    -   Chemical Resistance: Chemical resistance of a protective layer        was evaluated by a rubbing test using a cloth moistened with        methanol.        <Examples Concerning Proximity Exposure>

Example 9

A transfer sheet was prepared in the same manner as in Example 1, exceptthat the surface of the PET film used as the support was processed so asto have a ten-point mean roughness of 0.48 μm. The emulsion surfaceprotective layer of the transfer sheet thus prepared was transferred toa photomask having a glass substrate, thereby making a protectivelayer-covered photomask.

Example 10

A transfer sheet was prepared in the same manner as in Example 1, exceptthat the surface of the PET film used as the support was processed so asto have a ten-point mean roughness of 0.24 μm. The emulsion surfaceprotective layer of the transfer sheet thus prepared was transferred toa photomask having a glass substrate, thereby making a protectivelayer-covered photomask.

(Patterning of Dry Film)

A 40 μm-thick photosensitive coating of a dry film (VANX F-340, tradename, a product of Fuji Film Olin Corp.) was transferred to a blue sheetglass having a thickness of 2 mm by using a laminator VA700 (made byTaisei Laminator Co., Ltd.) under conditions that the roll temperaturewas 100° C., the transfer pressure was 0.3 Mpa and the transfer speedwas 1 m/min.

Via each of the protective layer-covered, glass substrate-typephotomasks prepared in Examples 1, 9 and 10, the photosensitive coatingwas subjected to proximity exposure (exposure under a condition that aslight distance was kept between the photomask and the subject). In thisexposure process, a 500 W ultrahigh-pressure mercury lamp (made by UshioInc.) was used as light source and the integrated amount of exposure at365 nm was adjusted to 40 mj/cm². And the photomask used therein hadpatterns in 25 μm width. After the exposure, each photosensitive coatingunderwent alkali spray development, and thereby patterns were producedtherein. The surface roughness (Rz) measurements of the plastic filmswere made with a three-dimensional surface roughness analyzer,Surfcoader SE-30K (made by Kosaka Laboratory Ltd.).

The evaluation of the patterns obtained are shown in Table 3.

TABLE 3 Surface roughness of support (PET film) (Rz: 10-point meanReproducibility roughness with respect to the of patterns in Examplereference length of 0.3 mm) dry film Example 1 0.9 × 10⁻² μm excellentExample 9 1.4 × 10⁻² μm good Example 10 5.6 × 10⁻² μm poor (the patternsproduced had uneven surface)

When the PET films having excellent surface smoothness were used as thesupport, the emulsion surface protective layers transferred onphotomasks had good surface properties and ensured reproduction of goodpatterns even in the case of proximity exposure. On the other hand, whenthe PET film inferior in surface smoothness (the Rz value of which wasgreater than 5.0×10⁻² μm) was used as the support, asperities in theshape of crater were formed at the surface of the dry film-originatedphotosensitive coating after development to result in poorreproducibility of patterns. As a cause of this result, it is supposedthat, when the support surface was rough, the surface of the emulsionsurface protective layer transferred on the photomask was roughened andthe refraction of ultraviolet rays occurred upon exposure to produce abad influence on patterning of the photosensitive coating.

Industrial Applicability

The present transfer sheet enables easy transfer without applying heator a solvent to a subject because, at time of transferring to a subjectsurface, tentative bonding is performed first with the aid of adhesionof the adhesive layer and then complete bonding is effected byirradiation with ionized radiation. Further, as the adhesive layercontains both a monofunctional (meth)acrylate and a low-viscosityionized radiation curable resin made up of polyfunctional (meth)acrylateunits, the protective layer formed can have excellent scratchresistance, close adhesion to an emulsion surface and high chemicalresistance. Therefore, the present transfer sheet is effectiveespecially in forming a protective layer for protection of the emulsionsurface of a photomask.

Moreover, the present protective layer-covered photomask obtained byusing the present transfer sheet can be used consistently for a longtime because the photomask is provided with the protective layerexcellent in not only optical characteristics but also scratchresistance and close adhesion.

1. A photographic emulsion surface protective layer transfer sheet,which comprises: a support having at least one surface withreleasability and, on the side of the support having that surface, aphotographic emulsion surface protective layer which is adhesive and inan uncured state, wherein the photographic emulsion surface protectivelayer in an uncured state comprises an ionized radiation-curable resincomposition containing a hydrophilic group-containing monofunctional(meth)acrylate and a polyfunctional (meth)acrylate.
 2. A photographicemulsion surface protective layer transfer sheet as described in claim1, wherein the photographic emulsion surface protective layer in anuncured state further comprises a thermosetting resin, an wherein theionized radiation curable resin composition contains, as maincomponents, a hydrophilic group-containing monofunctional (meth)acrylateand a polyfunctional (meth)acrylate having an acryloyl group number ofat least
 3. 3. A photographic emulsion surface protective layer transfersheet as described in claim 1, wherein the photographic emulsion surfaceprotective layer in an uncured state further contains at least onepolyamine selected from polyamines containing primary or secondary aminogroups.
 4. A photographic emulsion surface protective layer transfersheet as described in claim 2, wherein the ionized radiation curableresin composition is contained in a proportion of from 60 weight % to 85weight % in the photographic emulsion surface protective layer in anuncured state.
 5. A photographic emulsion surface protective layertransfer sheet as described in claim 1, wherein the hydrophilicgroup-containing monofunctional (meth)acrylate is contained in aproportion of from 20 weight % to 55 weight % in the photographicemulsion surface protective layer in an uncured state.
 6. A photographicemulsion surface protective layer transfer sheet as described in claim1, wherein the hydrophilic group-containing monofunctional(meth)acrylate is a monofunctional (meth)acrylate containing at leastone carboxyl group.
 7. A photographic emulsion surface protective layertransfer sheet which comprises: a support having at least one surfacewith releasability and, on the side of the support having that surface,a photographic emulsion surface protective layer which is adhesive andin an uncured state, wherein the photographic emulsion surfaceprotective layer in an uncured state comprises an ionizedradiation-curable resin composition containing a hydrophilicgroup-containing monofunctional (meth)acrylate and a polyfunctional(meth)acrylate, and wherein the photographic emulsion surface protectivelayer in an uncured state has a curing index (I) represented by thefollowing equation in the range of 80 to 300:I=R 1×S 1+R 2×S 2+ . . . +Rn×Sn wherein I is a curing index; R1, R2, . .. , Rn are percentages by weight of resin components (resin 1, resin 2,. . . , resin n), respectively, in the photographic emulsion surfaceprotective layer in an uncured state; and S1, S2, . . . , Sn areacryloyl group numbers of resin components (resin 1, resin 2, . . . ,resin n), respectively, in the photographic emulsion surface protectivelayer in an uncured state.
 8. A photographic emulsion surface protectivelayer transfer sheet as described in claim 1, further having at leastone cure layer between the support surface and the photographic emulsionsurface protective layer in an uncured state.
 9. A photographic emulsionsurface protective layer transfer sheet as described in claim 1, whereinthe support has a surface roughness of 5.0×10⁻² μm or below in terms often-point mean roughness with respect to a reference length of 0.8 mm asdefined in JIS-B-0601.
 10. A method of forming a photographic emulsionsurface protective layer, comprising (1) bonding a photographic emulsionsurface protective layer transfer sheet as described in claim 1 to anemulsion surface so that the photographic emulsion surface protectivelayer in uncured state is brought into contact with the emulsionsurface, (2) curing the photographic emulsion surface protective layerin an uncured state by irradiation with ionized radiation from thesupport side and, at the same time, making the photographic emulsionsurface protective layer adhere to the emulsion surface, and (3) peelingoff the support of the transfer sheet and leaving the emulsionprotective layer alone on the emulsion surface.
 11. A protectivelayer-covered photomask, which comprises a photomask and, thereon, aphotographic emulsion surface protective layer formed by use of a methodas described in claim
 10. 12. A protective layer-covered photomask asdescribed in claim 11, wherein the photographic emulsion surfaceprotective layer has a pencil hardness of at least H as measured inaccordance with the pencil scratch test defined in JIS K-5400.
 13. Aphotographic emulsion surface protective layer transfer sheet asdescribed in claim 1, wherein the support is a plastic film containing,as a main component, polyethylene terephthalate, polypropylene,polyvinyl chloride, polystyrene, polycarbonate, or triacetate.
 14. Aphotographic emulsion surface protective layer transfer sheet asdescribed in claim 1, wherein the support has a thickness of from about20 μm to about 150 μm.
 15. A photographic emulsion surface protectivelayer transfer sheet as described in claim 1, wherein the support has alayer of release agent on the surface contacting the photographicemulsion surface protective layer.
 16. A photographic emulsion surfaceprotective layer transfer sheet as described in claim 15, wherein therelease agent is a coating of silicone, teflon, urethane resin, melamineresin, fluorocarbon resin, silicone resin, polyester resin, polyolefinresin or a mixture thereof having a dry thickness of 0.1 to 5 μm.
 17. Aphotographic emulsion surface protective layer transfer sheet asdescribed in claim 1, wherein the support has an ionized-radiationtransmittance of at least 50%.
 18. A photographic emulsion surfaceprotective layer transfer sheet as described in claim 1, which furthercomprises, on the side of the photographic emulsion surface protectivelayer opposite the support, a separator layer which is a film of aplastic or a paper coated with a release agent.
 19. The method of claim10, wherein the bonding and curing of the photographic emulsion surfaceprotective layer is conducted without heating or application of asolvent.
 20. A photographic emulsion surface protective layer transfersheet as described in claim 8, wherein the cure layer is a cured resinfrom a composition comprising a hydrophilic group-containingmonofunctional (meth)acrylate and a polyfunctional (meth)acrylate.